Ashley Ahearn

International leaders gathering in Paris to address global warming face increasing pressure to tackle the issue of "climate refugees." Some island nations are already looking to move their people to higher ground, even purchasing land elsewhere in preparation.

In the U.S. Northwest, sea-level rise is forcing a Native American tribe to consider abandoning lands it has inhabited for thousands of years.

Washington state is home to more glaciers than any other state in the lower 48, and they're receding faster than ever before. That's a problem for the Pacific Northwest, where glaciers are crucial for drinking water, hydropower generation and salmon survival.

Across the Western U.S., yearly areas of snowpack are decreasing, and researchers are trying to figure out what that means for everything that relies on the snowmelt — from farms to power plants to a little creature known as the Cascades frog.

It's about 25 degrees on a clear Saturday morning when Gregg Treinish — executive director of Adventurers and Scientists for Conservation, a nonprofit that puts volunteers to work gathering data for scientists around the world — gathers a small group of outdoor adventurers around him near the Duckabush River in the Olympic National Forest in Washington state.